[AArch64][SVE] Implement PFALSE with explicit AArch64ISD node.

The ISel patterns for PFALSE helps recognise the instructions as being
free of side-effects, which helps MachineCSE remove redundant
PFALSE instructions.

Reviewed By: dmgreen

Differential Revision: https://reviews.llvm.org/D118054

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -2200,6 +2200,7 @@ const char *AArch64TargetLowering::getTargetNodeName(unsigned Opcode) const {
     MAKE_CASE(AArch64ISD::INSR)
     MAKE_CASE(AArch64ISD::PTEST)
     MAKE_CASE(AArch64ISD::PTRUE)
+    MAKE_CASE(AArch64ISD::PFALSE)
     MAKE_CASE(AArch64ISD::LD1_MERGE_ZERO)
     MAKE_CASE(AArch64ISD::LD1S_MERGE_ZERO)
     MAKE_CASE(AArch64ISD::LDNF1_MERGE_ZERO)
@@ -9984,7 +9985,7 @@ SDValue AArch64TargetLowering::LowerSPLAT_VECTOR(SDValue Op,
     // lowering code.
     if (auto *ConstVal = dyn_cast<ConstantSDNode>(SplatVal)) {
       if (ConstVal->isZero())
-        return SDValue(DAG.getMachineNode(AArch64::PFALSE, dl, VT), 0);
+        return DAG.getNode(AArch64ISD::PFALSE, dl, VT);
       if (ConstVal->isOne())
         return getPTrue(DAG, dl, VT, AArch64SVEPredPattern::all);
     }

llvm/lib/Target/AArch64/AArch64ISelLowering.h

@@ -323,6 +323,7 @@ enum NodeType : unsigned {
   INSR,
   PTEST,
   PTRUE,
+  PFALSE,
 
   BITREVERSE_MERGE_PASSTHRU,
   BSWAP_MERGE_PASSTHRU,

llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td

@@ -730,7 +730,7 @@ let Predicates = [HasSVEorStreamingSVE] in {
   defm BRKBS_PPzP : sve_int_break_z<0b110, "brkbs", null_frag>;
 
   def PTEST_PP : sve_int_ptest<0b010000, "ptest">;
-  def PFALSE   : sve_int_pfalse<0b000000, "pfalse">;
+  defm PFALSE  : sve_int_pfalse<0b000000, "pfalse">;
   defm PFIRST  : sve_int_pfirst<0b00000, "pfirst", int_aarch64_sve_pfirst>;
   defm PNEXT   : sve_int_pnext<0b00110, "pnext", int_aarch64_sve_pnext>;
 

llvm/lib/Target/AArch64/SVEInstrFormats.td

@@ -334,6 +334,8 @@ multiclass sve_int_ptrue<bits<3> opc, string asm, SDPatternOperator op> {
 
 def SDT_AArch64PTrue : SDTypeProfile<1, 1, [SDTCisVec<0>, SDTCisVT<1, i32>]>;
 def AArch64ptrue : SDNode<"AArch64ISD::PTRUE", SDT_AArch64PTrue>;
+def SDT_AArch64PFalse : SDTypeProfile<1, 0, [SDTCisVec<0>, SDTCVecEltisVT<0, i1>]>;
+def AArch64pfalse : SDNode<"AArch64ISD::PFALSE", SDT_AArch64PFalse>;
 
 let Predicates = [HasSVEorStreamingSVE] in {
   defm PTRUE  : sve_int_ptrue<0b000, "ptrue", AArch64ptrue>;
@@ -609,6 +611,15 @@ class sve_int_pfalse<bits<6> opc, string asm>
   let isReMaterializable = 1;
 }
 
+multiclass sve_int_pfalse<bits<6> opc, string asm> {
+  def NAME : sve_int_pfalse<opc, asm>;
+
+  def : Pat<(nxv16i1 (AArch64pfalse)), (!cast<Instruction>(NAME))>;
+  def : Pat<(nxv8i1 (AArch64pfalse)), (!cast<Instruction>(NAME))>;
+  def : Pat<(nxv4i1 (AArch64pfalse)), (!cast<Instruction>(NAME))>;
+  def : Pat<(nxv2i1 (AArch64pfalse)), (!cast<Instruction>(NAME))>;
+}
+
 class sve_int_ptest<bits<6> opc, string asm>
 : I<(outs), (ins PPRAny:$Pg, PPR8:$Pn),
   asm, "\t$Pg, $Pn",

llvm/test/CodeGen/AArch64/sve-pfalse-machine-cse.mir

@@ -0,0 +1,26 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -run-pass=machine-cse -mtriple=aarch64 -mattr=+sve -o - %s | FileCheck %s
+---
+name:            pfalse
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $p0
+
+    ; CHECK-LABEL: name: pfalse
+    ; CHECK: liveins: $p0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:ppr = COPY $p0
+    ; CHECK-NEXT: [[PFALSE:%[0-9]+]]:ppr = PFALSE
+    ; CHECK-NEXT: [[UZP1_PPP_B:%[0-9]+]]:ppr = UZP1_PPP_B [[COPY]], [[PFALSE]]
+    ; CHECK-NEXT: [[UZP1_PPP_B1:%[0-9]+]]:ppr = UZP1_PPP_B killed [[UZP1_PPP_B]], [[PFALSE]]
+    ; CHECK-NEXT: $p0 = COPY [[UZP1_PPP_B1]]
+    ; CHECK-NEXT: RET_ReallyLR implicit $p0
+    %0:ppr = COPY $p0
+    %2:ppr = PFALSE
+    %3:ppr = UZP1_PPP_B %0, %2
+    %4:ppr = PFALSE
+    %5:ppr = UZP1_PPP_B killed %3, %4
+    $p0 = COPY %5
+    RET_ReallyLR implicit $p0
+...